Several types of dryer fabric softeners have been available. One type of dryer fabric softener is available as a dryer sheet. The dryer sheet is placed in the dryer along with wet laundry. The sheet is often a nonwoven fabric containing a solid composition that includes a fabric softener and a fragrance. During the drying cycle, the temperature increases as the laundry dries, causing the fabric softener to melt and transfer from the nonwoven sheet to the laundry. Dryer sheets are generally provided for a single use. If the dryer sheet becomes entangled with an article of laundry, excessive deposition onto that piece of laundry may result in “spotting.” Spotting is the condition where concentrated fabric softener causes a dark spot on a laundry item. For certain dryer sheet products, it is believed that dispensing of the fabric softener is primarily caused by the heat of the dryer melting the fabric softener on the dryer sheet. It is believed that this mostly takes place near the end of the drying cycle when the temperature within the dryer increases.
There are other U.S. patents that describe dryer sheets containing fabric softeners. U.S. Pat. No. 3,442,692 to Gaiser; U.S. Pat. No. 3,686,025 to Morton; U.S. Pat. No. 4,834,895 to Cook et al.; U.S. Pat. No. 5,041,230 to Borcher, Sr. et al.; and U.S. Pat. No. 5,145,595 to Morris et al.
Another type of dryer fabric softener is available as a pouch containing a fabric softener composition. The pouch can be attached to the dryer drum. During the drying cycle, the increase in temperature can melt a portion of the composition inside the pouch. The melted composition then passes through the pouch and transfers to the laundry. The pouch type dryer fabric softener can be available for multiple uses. An example of the pouch type dryer fabric softener was available under the name “Free 'Soft” from Economics Laboratory of St. Paul, Minn. Examples of pouch type dryer fabric softeners are disclosed by U.S. Pat. No. 3,870,145 to Mizuno; U.S. Pat. No. 3,967,008 to Mizuno et al.; and U.S. Pat. No. 4,098,937 to Mizuno et al.
Yet another type of dryer fabric softener is disclosed in U.S. Pat. No. 7,087,572 to Hubig, et al. The dryer softener composition is in the form of a solid that, in the heat of the dryer, transfers softening agents to the fabric. U.S. Pat. No. 7,087,572 is herein incorporated by reference in its entirety. As one can readily appreciate, due to venting a dryer to the outside, the inside of a dryer is directly open to the external air. When not in use the internal temperature of a dryer often approaches the outside temperature. In extreme conditions such as is found in the winter, exterior temperatures often drop below zero degrees Fahrenheit. In contrast, when a dryer is in operation, the internal temperature is much higher and the internal fabric temperature in a consumer dryer may reach up to about 160 degrees Fahrenheit. It has been found that anything placed inside the dryer, including a solid fabric softener, is subjected to extreme temperature swings. Applicants have learned that due to such extreme temperature swings, the stability of the solid fabric softener may be compromised. The solid dryer fabric softener may crack, crumble and even separate from its attachment. Such cracking, crumbling, and separation results in reduction of the overall useful life of the solid softener and can result in yellowing of the fabric, or deposition of marks on the fabric including spotting or streaking.
It was surprisingly discovered that by adding silicone to the composition of solid dryer fabric softeners, numerous advantages resulted. The solid dryer softeners exhibited thermal stability both during manufacture and during use in a dryer. Such thermal stability resulted in increased product performance and reduced probability of cracking and crumbling during use. In addition, the silicone-enhanced solid dryer softeners imparted desirable traits on the fabrics including, but not limited to, increased softness, reduced static, reduced wrinkling, reduced yellowing, and increased absorbency. The reduced yellowing occurred both in the solid dryer softener product and in the fabrics dried in its presence. Additionally, reduced streaking and/or spotting of the softener on fabrics occurred with the addition of silicone. Moreover, no deleterious aspects were noticed upon adding silicone to the solid dryer softener composition. The dispense rates found in the solid dryer softeners remained consistent whether or not silicone was added to the composition.
While it has been known to add silicones to fabric softeners for anti-wrinkling purposes, it has not previously been known to add silicones to solid dryer softeners resulting in the above-cited attributes.
Additional fabric softener compositions are disclosed by U.S. Pat. No. 3,972,131 to Rudy et al. and U.S. Pat. No. 4,035,307 to Fry et al.